New device for saphenous vein-to-aorta proximal anastomosis without side-clamping

Many years ago an unclampable aorta forced me to stop extracorporeal circulation for every aortic bite during the proximal anastomosis. At the same time, I had to cover the hole with a finger while the pump was resumed repeatedly during every bite to the vein. Immediately I looked for something to block or curtail the loss of blood.

At first I prepared a steel bar of 5 mm in diameter for insertion in the aortic hole, with a lateral furrow to take the needle for the suture (object 1)(Figure 3). I thought that in critical cases of unclampable aorta rather than go to a hypothermic circulatory arrest otherwise required in these patients [11], I could try to perform the anastomosis even if a stream of blood flowed through the lateral furrow of the bar. After trying unsuccessfully to make some stitches, I realized that many problems needed to be solved. First the furrow was too large. It would have to become a narrow slit so that it could transform the stream of blood into a sharp jet. Second the bar should have a rest-point to understand where the end into the aorta was. Third, I realized that instead of doing the traditional suture where the needle enters the aortic hole first to pass the aortic wall from inside to outside, using a slit-object the needle has to enter the aortic wall first and to exit through the aortic hole and through the slit. Even if diseased, the aortic wall retains a minimum of elasticity, which allows the needle-holder to press the wall, push the tip of the needle against the bar into the furrow and rotate the needle just enough to drive the tip out. On the other hand, it would be ineffective to press the needle-holder against the steel bar. I also realized that it would be useful to use the 5-0, half-circle needle rather than the usual 6-0, 3/8 one. Then, I looked for a bar with a ball. I found it through the plumber in the hospital (object 2). A slit was made in the ball to receive the needle (Figure 4). However, it did not work because it was impossible to grasp the tip of the needle and so the idea was abandoned. Nevertheless, I learned that the blood-jet from the slit could be easily controlled if it was thin, clear and sharp (Figure 5).

When I used some of the devices introduced by the manufacturers to facilitate proximal anastomosis, I realized that the cost was very high and they were not easy to use. It seemed to me they were not easier to handle than an object with a sharp jet of blood. Therefore, I returned to my original idea. I thought that if I scooped out the ball I could probably grasp the tip of the needle.

On 14^th January 2006 the Ethics Committee of Azienda Ospedaliera "C. Poma", Mantua, gave me written consent to develop the instrument for proximal anastomosis, which we named "Slit Device". At first I prepared a scooped out ball like a little spoon with a slit (object 3) (Figure 6). It did not work because it did not remain fixed over the hole. Even if it seems somewhat simple, I learned that the object must have a 5 mm appendage that enters the aortic hole, as the previous bar did. Moreover, it should have an enlargement to give an adequate weight so that it could be abandoned without being pushed out of the hole by the blood pressure. The same enlargement would be useful to stop the blood jet. After this, I incorporated all these reflections in a drawing from which the device has been developed by hand by an experienced mechanic (Figure 7). The next object (object 4) was too heavy and cumbersome (Figure 8). Later, another (object 5) was much better and was used eventually with good results for one vein-to-aorta anastomosis on a patient with a diseased wall of the aorta (Figure 9 – 10). After this test, I realized that the slit in the appendage had to be flared to drive the needle more easily. I also realized that the object did not need to look like a spoon, which was the remnant of the idea of the scooped-out ball. With a new simplified shape (object 6) so that a mechanism could be implemented in the future to reduce the blood jet, some other patients were satisfactorily treated (Figure 11, 12, 13). The latter were on-pump patients because the slit of the horizontal plate was too large, yet.

Seven different objects were made. The first two objects were provided from the plumber of the hospital. The first was of simple steel and the second of brass. They were sterilized to try one stitch only but they were unusable. After the Ethic Committee's consent, all other objects for testing were made of stainless steel 316L. The object 5 was used to complete the first anastomosis (Figure 14). The object 6 has proven to be useful in selected cases. The last object, with the appendage curved a little, was carved out by a laser machine but has not been tested yet. However, the definitive device should be made of plastic so that the slit of the horizontal plate could be even more narrow. In this case the horizontal plate could be progressively thinner near the slit so that when doing the stitches the needle could force the slit and, at the same time, the blood jet would be reduced again. Some other simple mechanisms to control the blood through the slit are under study and patent.

Slit Device is not a routine instrument. It is only an alternative to the other two manual anastomotic devices, with the same surgical indications: avoiding aortic clamping in the case of aortic disease. Similarily, when using them, some variations have to occur in surgical practice. First, the direction of the suture, i.e. the direction of the bites of the needle, is different in that the needle enters the aortic wall from the adventitia towards the intima. After that, the tip of the needle knocks against the flared appendage of the object, the flare drives it into the slit, then the needle is rotated by the needle-holder until the tip comes out through the slit of the device so that it could be grasped by the forceps or the needle-holder(Figure 15). A 5-0 half circle needle is needed, thus bigger than usual. This needle has a 90 cm long thread to allow distant suture (parachute technique). Near the end of the suture the device is removed, a finger stops the blood, the two arms of the thread are pulled, the vein is brought close, the coils of thread are pulled by a hook and finally the last stitch is whipped in. Alternatively, to lose as little blood as possible through the slit in off-pump patients, you could apply only four single separate stitches at the four cardinal points of the aortic hole using the device, then remove the device stopping the hole with your finger, pass the same four stitches in the vein graft, bring the vein graft closer removing the finger and pull the four separate threads by four thin, soft tourniquets so that the aortic hole is covered by the vein. Then whip the remaining stitches in as needed and tie them, release the four tourniquets and finally tie the first four stitches. In this way the anastomosis is performed by a less conventional interrupted suture instead of the usual running one (Figure 16).

Like the other one, Slit Device has many advantages and some problems. An important characteristic is that nothing is deployed into the aorta. The device is only placed on the aorta with the small appendage slipped into the hole. Its main advantage is that manipulation of the aorta is avoided, no foreign bodies are incorporated in the suture and, most importantly, the aortic intima is not touched at all. The advantages are listed in Table 2.

Even though there is no extensive clinical experience a disadvantage seems to be the need for manual dexterity for the rapid blind manoeuvres – scalpel, finger, punch, finger, device – which are the same with many other devices. Indeed, the main drawback of the device is the blood jet from the slit so that the blood pressure has to be lowered by vasodilators during the anastomosis. However, sudden jets of blood which are not sharp, not well directed, not predictable as with the Slit Device are frequent with other devices, too. Other disadvantages are listed in Table 3.

Thus, Slit Device belongs to manual anastomotic devices, such as Enclose II and Heartstring, but its function is completely different. It is not a sophisticated device like them. Nevertheless, like the others it could be safer than the partial occluding clamp in off-pump patients, too [13]. Slit Device can be useful in patients with severe atherosclerotic disease of the ascending aorta where a clamp cannot be applied.